Slightly increase the epsilon value for margin computation frequency,  many type 2 systems (on Windows, 32 bit pythonxy, but not on 64 bit Linux which I tested on) got cross over margins calculated at frequencies  around 1e-11
Slightly increase the epsilon value for margin computation frequency, 
many type 2 systems (on Windows, 32 bit pythonxy, but not on 64 bit Linux
which I tested on) got cross over margins calculated at frequencies 
around 1e-11


roryyorke/python-control,python-control/python-control,murrayrm/python-control